Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/99b6e505a0397a69dfa82158ffd7b6a5.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563